The Collaborative International Dictionary of English v.0.48:

Reward \Re*ward"\, v. t. [imp. & p. p. Rewarded; p. pr. & vb.
   n. Rewarding.] [OF. rewarder, another form of regarder, of
   German origin. The original sense is, to look at, regard,
   hence, to regard as worthy, give a reward to. See Ward,
   Regard.]
   To give in return, whether good or evil; -- commonly in a
   good sense; to requite; to recompense; to repay; to
   compensate.
   [1913 Webster]

         After the deed that is done, one doom shall reward,
         Mercy or no mercy as truth will accord.  --Piers
                                                  Plowman.
   [1913 Webster]

         Thou hast rewarded me good, whereas I have rewarded
         thee evil.                               --1 Sam. xxiv.
                                                  17.
   [1913 Webster]

         I will render vengeance to mine enemies, and will
         reward them that hate me.                --Deut. xxxii.
                                                  41.
   [1913 Webster]

         God rewards those that have made use of the single
         talent.                                  --Hammond.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rewarding
    adj 1: providing personal satisfaction; "a rewarding career as a
           paramedic" [ant: unrewarding]

Moby Thesaurus II by Grady Ward, 1.0:

64 Moby Thesaurus words for "rewarding":
   advantageous, affable, agreeable, amiable, amicable, blissful,
   cheerful, compatible, compensating, compensative, compensatory,
   complaisant, congenial, cordial, desirable, dulcet, en rapport,
   enjoyable, enriched, enriching, fair, fair and pleasant, felicific,
   felicitous, fine, fruitful, gainful, genial, good, goodly,
   gracious, grateful, gratifying, harmonious, heart-warming, honeyed,
   likable, lucrative, mellifluous, mellow, moneymaking, nice,
   of value, paying, pleasant, pleasing, pleasurable, pleasure-giving,
   pleasureful, productive, profitable, remunerative, reparative,
   repaying, retributive, retributory, rewardful, satisfying, sweet,
   valuable, welcome, well-spent, worthwhile, yielding a return