In the interests of total fairness (and donning a flameproof suit) I think you need to consider the following:
1) Only go with a reputable company who have a (very) strong customer reputation to consider, or a company who has built up a rep the hard way, for example, Superchips, APR, Revo have gold standard brands to protect and customer reputation to protect, shark have an awesome rep as an up and coming working hard to build their rep tuner
2) Only go with a company that has great feedback from many users, all above have that (yes everyone of them has customers with niggles (excepting have heard nothing bad about shark but don't have the installed base of SC, APR and Revo all of whom have a few bad press comments which is going to happen when many cars out there prob have hidden issues that only come to light when you rechip but by and large have a very large and very happy customer base) )
3) Ideally decide where you want to end up before you start, i started with superchips (which IMHO are great for modest modification levels and have a great rep with K04 cars with higher levels of mods) because I only wanted a software upgrade on my K03 car I loved the bluefin and the lower cost, and then went for CAI, TBE and HPFP (so with 20:20 hindsight should have probably went Revo from the start cause of fine tuning ability) but to be honest stage 2+ SC has made the power I wanted 275 HP, 315lbft rr on a independant who offer a different chipping manufacturer so believe them! (PSI tuning - in Stoke (newcastle under lyme actually top guys highly recommeded by me!))
4) Finally go with a local tuner who knows what they are doing and can offer a high quality local service / Back up, probably more important than any of above points (I bought my HFP from Dave at PDT, top guy just wish he was closer (really is very very helpful and knowledgeable and I would def trust my car / chip choice to him, JKM and Jabba also great reputations - which is nearest to you?) as I am in the South West / west mids border and he is in the North East and I am Glos, I went SC and PSI, But Dave offered to drive down from the North East, how good is that for service!).
Hope above helps and is more practical than the I love my chip, I make a zillion HP and beat everyone else on the dyno and the others are crap advice which is all too revalent on the forums ;-)
cheers
John (hides and awaits abuse)