It's often claimed that playing a 1st-level magic-user in old school Dungeons & Dragons stinks, because the character is so much weaker than other classes. That's not the case in OD&D, at least prior to Supplement I. At 1st level, all character classes have the same chance to hit and all have roughly the same range of hit points. Both the MU and the cleric get a single D6, while a fighting man gets 1d6+1 -- hardly much of a difference. Granted, clerics and fighting men can wear any armor and wield a larger selection of weapons, but magic-users get access to spells like charm person and sleep, both of which are quite effective in dealing with foes. Over time, the cleric and the fighting man outstrip the MU in terms of physical prowess. However, magic-user spells become increasingly potent and are as likely to turn the tide of battle as anything a fighter can bring to bear, if not moreso.
Anyway, it's been my experience of playing OD&D over the past year that magic-users are not noticeably weaker than other classes. They have their strengths and weaknesses, like any class, but the odds aren't stacked against them from the start, as some would claim. I find I rather like this state of affairs; it's one of the reasons I'm glad to be playing OD&D.