Not a bug, but some disadvantage: when long actions are performed, the GIU is frozen. For example, when my firewall blocked internet access for a new copy of fpcupdeluxe, and it tried to download something, GUI was just frozen forever. Maybe consider multi-threading?
Just successfully installed a fresh stable FPC+Lazarus and a fresh trunk versions, but only with option Auto-switch repo URL turned on. Without it, downloads failed.