PREVIEW-Boost, Pre give hope for otherwise weak Sprint

* Analysts expect Sprint to lose 1.1 mln postpaid users

* Analysts see Sprint adding 180,000 prepaid users

* Shares more than double in first quarter

By Sinead Carew

NEW YORK, May 1 (Reuters) - Sprint Nextel Corp (S.N) is expected to report first-quarter growth for its Boost prepaid unit but its traditional business is still seen suffering from mass customer defections due to the recession and a lingering reputation for poor customer service.

After several quarters of losing prepaid customers, who pay for calls in advance and do not commit to contracts, Boost's first-quarter launch of a $50-per-month unlimited service plan is seen to have helped Sprint add prepaid customers as cost conscious phone users are keener than ever on cheap deals.

"I think that will be an increasingly important part of the strategy," said UBS analyst John Hodulik referring to Boost.

Analysts expect net growth of about 185,000 Boost prepaid customers who pay for calls in advance, according to the average estimate of seven analysts polled by Reuters.

Estimates for prepaid range from a loss of 150,000 customers to a gain of 600,000 customers but everybody expects the new plan to at least help Sprint do better in the first quarter than its fourth-quarter prepaid loss of 314,000.