I flew with Emirates from Heathrow via Dubai and it was fine. One word of warning though - I took a one-night stopover in Dubai (highly recommended) so I had to get my bags and re-check in the following day. Collecting the bags took ages (had to wait about an hour for them to appear on the carousel) and then checking in the following morning was a nightmare - a HUGE queue. Other than that Dubai airport is fine - the biggest duty-free shop I've ever seen. Emirates staff were very friendly too.
By the way,
www.seatguru.com is a good way of checking out the legroom and seat layout on the various aircraft the different airlines use.
Martin