I have an '07 300 XC-W. As the note before said, I believe the '06 was the last year in the USA that it was called an EXC. The 2-s EXC's were NOT street legal in the US! Only difference is the EXC came with lights. The XC-W (and XC's) will accept the lights "plug & play" - they are already wired for it and have the stator to support it.
It depends on your state whether you can street register it. In NH its not a big deal for dualsporting them, fortunately for me. I need mine street plated for enduros and "turkey runs" (new england term for non-competitive enduro-type ride). I personally think it sucks on the road, but its awesome on the trails. 2-s don't like constant throttle riding (roads), and you can't "coast" them because they rely on the oil/gas mix to lube the top end of the engine. IMO, the 4-s EXC's are clearly better DS bikes, but I prefer the 300 for really nasty single track. It lugs lower than 4-s believe it or not, and as long as you use a tiny bit of throttle it will NOT stall (can't say that about 4-s). Do the mod's mentioned earlier (stiffer power valve spring, "softer" ignition map for '07+ bikes, and correct jetting) and throw a trials tire on it & you have an awesome technical terrain bike. One of the big reasons why some ppl shy away from this bike, is because if you make a mistake with the throttle in tight terrain it can get you in a world of hurt really fast. Those mods mentioned earlier, and a G2 throttle cam can make a big difference in controlling it in technical conditions.
The '08+ bikes with electric start can have the e-start removed; I know a handful of racers who did that. It doesn't weigh much so you're not gaining much by doing that. You can also retrofit the '08+ bikes (250 & 300 only) that came without the e-start. Its a nice to have, but not nearly as important as it would be on a 4-s. The 300's are very reliable starter, with usually 1 firm full kick. No 4-s drill to learn either...