Let me try to answer to the best of my knowlegde :-)
I didn't look much recently, but I also don't know any other NAS/router with such functionality - that's why I bought WL700gE :-)1- I can't find any real competitor to this product except for the Freecom 3-wlan that has no BT and is more expensive. Have I missed something?
This is true. But in the meantime, there is "hacked" firmware which is pretty easy to install which offers better functionality and has no limit in size of torrents.2- all the reviews write that files larger than 4 GB can not be downloaded and this might have to do with some firmware issue. Is it still the case? (the reviews are one year old)
Yes, it can be replaced, I dunno the exact procedure, it is somewhere on the forum, please search...3- Can the HDD be replaced by any IDE HD? for example a 750GB? What is the procedure for replacement?
It can be either in router's custom format if you want to use MIRROR functionality (to mirror the internal drive for backup purposes), or in FAT32. NTFS drives can be connected as read-only.4- USB HDD can be connected to the router. I have read that they had to be formated in FAT32, is that so?
Hm, hard to tell, but I think for printer, even 3-4m cable would work OK.5- How long can a USB cable be between the router and the HDD or a printer?
see here: http://www.usb.org/about/faq/ans5
regards,
Dalibor