I have been doing taekwondo for 3 and a half years now and I toltally agree about the lack of groundfighting. I also think its the practitioner and the style that suits him that counts, not just the style. I use taekwondo kicks and some jumping attacks, traditional boxing hands, muay thai knees and elbows and jumping attcks, and soon will be starting either jujutsu and/or bjj for the groundfighting. Im not trying to be a jack of all trades master of none, im just looking for things to complement tkdo and muay thai (my main styles). I think the bjj/jj will benifit me like boxing has.