I just replaced the water pump in our 94 960 with 176,000 miles due to leaking at the rear seal of the pump. I was told at the third timing belt interval that the pump would last to the fourth belt change. I found the pump impeller had receded to the rear and ate an 1/8 inch into the housing. I replaced the hydraulic tensioner , tensioner roller, and idler pulley also. This was 310.00us for all parts and a few hours of time. Cheap insurance to ward off a 1500.00us top end overhaul if the pump had seized. Be sure to have a 12mm offset wrench to get the lower tensioner bolt out.
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92 244 lowered, Bilsteins, IPD sways, Unitek cam/header, TSW Revo 18x8's - 94 965 Niiice MONEY PIT! - 76 Datsun 280Z lowered, modified head, cam, headers, intake

Yes, definitely. If the bearing goes bad in the water pump, you'll lose the timing belt. I highly recommend going with OEM on this part, as I had a GMB aftermarket pump eat itself within 20K miles. Luckily my low coolant light came on before the bearing completely disintegrated and threw off the belt. OEM is worth the extra cost for this part in my opinion. I'd rather spend an extra $40 to not have to spend a couple grand.
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Lance '92 965 w/ 200K miles

Agreed, at least the quality is consistent with OEM. That's not to say all aftermarket pumps are bad - just most of them. I'm sure there are some quality brands available for replacement but for peace of mind and convenience I just go to the dealership for water pumps.
-Chris

Having recently done a T-belt job on my new (to me) '95 960, I gotta say that the water pump is definitely one of those 'might as well' items on a timing belt job. It only takes an extra 15-20 minutes to swap out that pump, which is nothing relative to the amount of time you'll spend on that hydraulic tensioner. Since just about everything on the front of the motor has to come off anyway, it makes good sense to go ahead & swap out that pump too.

Ditto to that. I replaced mine (94 960) at 140k miles when I did the t-belt. I'd hate the thought of being stranded on a hot highway because I didn't replace the waterpump while I was in there anyway.

An ounce of prevention...

My experience of non-Volvo pumps has been poor. The GMB pumps that I put on my old 240 were garbage with a good warranty. Not worth it!

I put a factory pump on my 960 when I did the 70K service. Due to the age of the car, I thought the seal might go before the bearings did. I saw it as cheap peace of mind, especially since my daughter drives the car now.