My hunter character is now level 13 and I am definitely enjoying the single player game: Nice cartoony graphics, simple but enjoyable rpg elements, Fun shooter gameplay (with vehicles). The quests drive the story along nicely although there seems to be some gaps: I didn't find any quests between level 5 and 10 for example.
Multi-player is another story. The PC version's online matchmaking uses Game-spy and it is really bad. Apart from the fact that the listings are unhelpful making it hard to choose a game to join there appears to be a variety of connection problems that prevent me joining a game 9 times out of 10. I tried hosting my own games but nobody ever joined me so I suspect the connection issues work both ways.
A quick google revealed that my problems are widespread. The two most widely touted solutions involve either port forwarding or signing up to Game-ranger. The problem with port forwarding is that everyone joining a game has to do it which explains why a lot of Borderlands' game lobbies have the word "port" or something similar crammed into the very limited number of characters allowed for naming lobbies. I decided to try the game ranger route instead.
Signing up for a free "Bronze" Game ranger account is painless. I already have Xfire and Steam on this machine and Game Ranger does not seem to interfere with either but just in case I opted to manually start game ranger when required rather than have it start automatically with Windows. Borderlands is clearly a big hit for Gameranger - at this moment Borderlands accounts for 109 out of 270 game lobbies on the service. As a third party matchmaking service Gameranger doesn't give any in game information about the level of players or the quests they are working on. The description field is long enough to say something like: "Level 8 to 12, Doing Bonehead Mission" but many hosters don't bother which makes lobby selection a bit of a gamble. I decided to start my own lobby instead asking for anyone who wanted to join and help with level 11 missions. Once I set up the "room" as it is called Gameranger automatically launched the game and put me into multiplayer mode. I selected my character and started and was soon joined by several other players. Success.
The level of co-operation was pretty much as expected from a PUG group - including a player who only wanted to spar (he lost every time) and a level 36 character who insisted on power levelling me through a mission I wasn't even on. Nevertheless Gameranger does seem to have cracked the connection problems and has a sufficiently large Borderlands following for me to recommend it.
One thing that appears lacking in Gameranger is hotkey to access the Gameranger panel while in a game. Even if I tab out it tells me I cannot go back to Gameranger until I exit the game. That makes surfing between game lobbies a real nuisance so perhaps I am missing something. Gameranger's support information is pretty limited however leading me to suspect that it does exactly what it says it does and nothing more.