When used correctly, it is. If you take it, and just keep a group of like three guys, it's perfect. From there you have the high ground to shoot down into the Fishing Village and the Lighthouse. So your team should hold those two, and you should be able to defend it pretty well with just the guys at Suribachi alone. Not to mention you have anti-air support from there as well. Seriously, if 2-3 guys hold Suribachi and use it to fend off enemies from the Fishing Village and Lighthouse, the rest of your team should be able to hold 3 bases and win the game pretty easily.
Haven't played 1943 in about a week. Probably going to get some games in tomorrow.