I purchased a Futaba 4PX from a shop in Hong Kong this past spring. Before buying I played around with the one they had in the case. That one had a NiMH battery.

Got mine home and ordered a LiFe Battery. Went to replace it only to find a LiFe battery ALREADY there! Now what I'm really confused about was the Radio had a Charger (typical cheapo charger they would send with a NiMH pack) in the box which I didn't keep (Chinese plug and all). I had charged the battery before I left Hong Kong so I know it works with the LiFe in the transmitter.

Is there a US Charger that will work the same way? I'd love to not have to pull and charge the Transmitter pack.

I am sure it did work with the LiFe, because all NiMh chargers will charge lipos. However, it's not a good practice because of a lack of voltage cutoff and no way to balance.
You can actually revive lithium batteries with a NiMh charger if the voltage has dropped below the standard low voltage rates for a lithium chargers to recognize. But once the voltage is brought up to normal low voltage ranges, you should stop the charge and then continue it with a normal lithium charge.

I suppose the reason radio companies haven't integrated a balancing circuit inside the transmitters yet is probably due to liability with safety standards, taking into account a bad battery lithium can potentially burn your radio to the ground, and of course what ever the radio is contained within while it's at it.
Until these companies can create a fire proof housing that has the balance leads already installed, it's just not going to happen unless you do it yourself with some simple modifications. Such as mounting a female balance plug in a user/custom cut opening drilled into the transmitter case.
Finding a small charger is easy however. Here is one for your consideration>

small self contained Lipo/Life charger

I've decided to make the switch to the 4px from Ko ex1 kiy, I was wondering if anyone else had made the same switch and how they think the 4px is compared to the Ko propo also what is the smallest receiver available for the Futaba? I'm a bit concerned about the size difference between the Ko propo kr411/413 and the futaba receivers, the futaba rx seem to be a fair bit bigger from what I've found and are all the futaba rx's compatible with the 4px as it operates on fhss and fasst technologies? What seems to be the most popular all round receivers for these tx's? With Ko propo the decision was made for us as there were only 2 and both were really good but with futaba I'm confused as to all the different rx's and what the differences or advantages/disadvantages are thanks for any help and advice in advance

Both Ko propo and futaba utilize FHSS (frequency hopping spread spectrum) modulation, so your not going to see much, if any at all of difference in range or speed.
The FASST is a combination of FSSS (Horizon's Spektrum modulation) and FHSS (Futaba, Ko Propo, Airtronics modulation) if I understand the technology correctly, and that takes the best from both modulations and further enhances the bind and slightly smooths out the channel actuation for a more real time experience.
The problem with FASST is the expense to produce from what I understand and the benefits are negligible in the eye of the typical consumer, especially for ground vehicles.
With that being said, I own the included futaba R304SB Rx, and I don't see where anyone should have any worries about it being small enough to work in most anything past micros.
The size differences between the two listed are as follows>

Futaba R304SB (35.1 x 23.2 x 8.5mm)

KO Propo KR-413FH (28 x 18.3 x 18.5mm)

And a pic of both

I ran a KIY since they first released in Japan several years ago it was a great radio that was very adjustable and very comfortable. A few months ago I decided to switch to the 4px. The feel is the same, I can't tell any difference on speed (at least not on 1/8 off road) the Rx is a little bigger but it usually fits better in all the radio boxes as it's not as tall. I no longer have any issues with the Rx's "popping crystals" I run the 304 Rx's that came with the radio in all vehicles. I was a little concerned that they were so cheap compared to KO but so far I have been very pleased with the radio. According to futaba the new 304 fhss is the fastest Rx. It's also the newest Rx.

Installing the tilt and drop down takes time and patience, I do miss the snap in design of the KIY. I no longer have the delicate issues that the KIY had, Rx, radio antennae, steering pots. I do find the 4px screen very bright at night and sometimes distracting on the stand, but there's a setting to let it dim. Overall I am very happy with the switch. I swapped my sons KIY out for a 4pls, it fits his hand better than the 4px hes 8 and I can use it as a back up with the 304 Rx's. The 4px will not run on lipo which seems backwards to me but a couple of $20 life packs work well.

Is anyone successfully running 1.2E firmware without issues?

I am running 1.2e with no issues. The problem i thought may have been an rx problem was actually a faulty esc.

My son and myself have been running 1.2E since it was released without issue as well. Iv also updated another 3 radios with 1.2E with no complaints.

I m running 1.2E without problems,its been running perfect, i ve updated my friend's newly bought 4px as well without any problems.

Thanks guys, just flashed mine with 1.2E as well.

stupid question here
i was always good in pointing and coreckting my buggy in the air with steering and throtle/brake.
sins i came from a sanwa m12 to my 4px i seem to be lost in this .
same buggy same servo and all .but cant get it right with steering corections in the air.
is it me or could it be the respons speed diferents?

It seems like you forgot how to drive lol j/k. The m12 from the factory comes trigger ratio forward 70% brakes 30% the futaba comes 50/50 factory. i change to 70/30 on my futaba and it seems it help me get the same feeling as the m12. But that was just me. Maybe that will help you to.

thanks wil try that also.

I also drive 70/30 on the 4PX as I came from Sanwa.
Than the feeling is the same as Sanwa.

Thank you very much for posting this information; I had the same exact issue. The strange thing is my 4PX started doing this after only 4 months. I only run on-road and always keep my radio in its case, so I'm not sure how this got dirty enough to impact performance already. Everything looked spotless inside. My old Magnum PCM is over 20 years old and doesn't have this issue Anyway, thanks again, this issue had me baffled until I saw your post.