Theres no question that it is an improvement over the T1 and for anyone that wants the latest innovation in sound realism this has to be a tempting proposition. If you already have a tyros1 and have done extensive personal work, registrations , patterns etc it makes sense to keep the compatability issues to a minimum but is the cost of the new sounds (the difference in styles is minimal in my view ) and improved functionality , hardisk recorder etc worth the extra investment ? Even the styles that have been reworked and had new mega voices added to them still sound like the old styles and the difference is only really noticeable when you put the old board and the new board together. Lets face it Yamaha did an excellent Job the 1st time with T1 andthe improvement in T2 is marginal. If they had completely done new styles altogether then this would have been a much more value for money proposition.
Its a tough call. Its an easier decision to make for someone that did not own the T1 as on its own merrits the T2 is an outstanding keyboard for sure.