I'm basically a rookie, so don't have expert opinion, but here's my $0.02:
Injector... Bought this one for $25. Have tried it a couple of times, not sure I can tell a difference. Think I do better brining birds and marinating four legged entrees. This is nice heavy duty SS, good tight screwed on cap, two needles, one with one big exit ole, other wih several small holes all the way down the shaft. One with he small ones would require completely thin, watery liquid. Sorry, not much help here.
http://www.amazon.com/exec/obidos/ASIN/B00DLWOCVC/tvwb-20
Thermapen vs lower priced imitations? I'm stuck on that one too. I'm at the "paralysis by analysis" point on that one. The CDN ones looks good, but have read a few not so great reviews. Will probably break down and get a Thermapen, but not in a huge hurry, so may hope for a SALE somewhere. The Thermapen seems to be universally loved, with only downside being the price. Think I'd rather drop 100 on something that should be top shelf with no concerns, opposed to 60-70 for similar product that might not be up to snuff. Grandpa always told me "if you're gonna be a bear, might as well be a grizzly"... Translates to "go big or go home"... Or "can't run with the big dogs, stay n the porch".
Remote-dual-prope thermo? Timing for me being in this market coincided with Maverick coming out with th ET-733. So I didn't have the dilemma of already having a 732 conflicting factor of getting the 733. I've used the Maverick about ten times maybe, and love it. I'm still learning to control my temperature, but can't imagine doing it without the Maverick. I'd recommend the 733 to anyone in the market. I read and read and read on this site, Amazon reviews, etc... And Maverick always came out highly rated. Only complaints that I read were people that didn't like unscrewing the battery compartment to install or replace batteries. I just don't see it as that big of a negative, as infrequently as you'll need to do it. I'm sure the screwed down lid seals better than a clip/slide in kind, but I suppose the screw could be bigger and easier to deal with.
In any case, you're in he right place to gather information, opinions and advice. The collective wealth of knowledge and experience on here is an incredible resource. I'm still feeling my way through most cooks, but have learned a ton from the good people here.