My DS1 was never a great sleeper but DS2 is even worse... he seriously wakes pretty much every hour - day or night - seems like he never really goes into a proper, deep, baby sleep...
he's 8mths now, got worse when he started teething but was never great before. very occasionally he might put together a 2hr sleep during the day but this is very rare - much more likely to be a 30-40min nap.
he also has a propensity to think that it's time to wake up from his night time sleep at all kinds of crazy hours - sometimes 2am, sometimes 4am. 5.30am counts as a sleep in in our house these days.
I have the feeling that this is just who he is - he's perfectly happy when he's awake - but on the off chance anyone else has had similar and found a solution other than waiting for them to (hopefully) grow out of it...