I was there and got a day of diving in. We ended up staying at the berjaya hotel because it was a family trip and the 4 star accommodation and a beach without sandflies were kind of important to the group. Me personally I would have been find in a 2 star chalet. Because we stayed at the berjaya it was easiest to just use their dive op, diving that day kinda sucked as currents were ripping and there was alot of suspended particle matter that reduced vis down to 20 ft or so, and overcast conditions didnt help, the day before we did some snorkling and conditions were much better. There are many good dive operations on the island, if you stay in tekek there is Tioman dive center and tioman reef divers which were both recommended to me, I also was recommended to use B&J's dive shop if I stayed on the north end of the island. I can only really comment on the berjaya dive op, it was a decent operation, but I felt like the Divemasters were zooming along a bit too quick, especially since members of our group were carrying as many as 3 cameras a piece and were crawling slowly looking for nudis and what not. If I ever went back I would probably try out Nazri's place and dive with B&J, especially to check out some of the deeper wrecks around the island.
as far as baggage I didnt know about the flexi tickets, and basically had my gear down to 10kg's in my check bagged, but my backpack(carry on) weighed almost 30kg, luckily they didnt weight the backpack, but buying the flexi ticket would have made life a little easier.