This is the third time I have done the Marlow half and would recommend it to anyone looking for a race with a fast course(with a few challenges), relaxed atmosphere, good organisation and spectator and family friendly
Swim is in the Thames, half upstream and half down. Plenty of space and loads of kayaks/ribs for safety
The bike goes from Marlow out towards Henley and up Pishill, which is a longish drag rather than a sharp climb, and then speedily(close to 40mph) down through Bix for the turnaround where you do another 2 laps. Well marshalled and sigposted throughout.
Run is along the Thames path, which is off road for a mile or so, then onto tarmac for the rest of the run. A few small little uphill sections with a downhill all the way back to transition. A quick 4 lap run.
Excellent facilities at the finish; immediate printout of times and splits, plenty of water and recovery drinks, cafe.
A good race to bring the family along to; kids park and ice cream van nearby, 4 chances to see competitiors on the run.
Only criticism was the water station on the bike wasn't very well manned or signposted; they missed me all 3 times